While last year's revelation that Apple slows down iPhones with aging batteries left a bad taste in users' mouths, the company's $29 battery replacement program was a step in the right direction. However, all good things must come to an end; Apple will soon shut down the program, leaving users to pay the full $79 to replace their faulty batteries.

To be clear, this change is coming to users whose iPhones are currently out of warranty. If you have an iPhone with a malfunctioning battery and still have either a one-year limited warranty or two-year AppleCare+ plan, your battery replacement should be free of charge, even after Apple kills the battery program (at least, until your warranty coverage expires).

When Is the Program Ending?

According to Apple, the company will be ending the battery replacement program on Dec. 31, 2018. After that date, out-of-warranty battery replacements will jump back up to $79, so you'll want to make sure you get yours replaced before then.

What iPhones Are Covered?

Unfortunately, not all iPhones are eligible for replacement. Apple is only honoring iPhones released in the past four years, which would include the following:

iPhone 6

iPhone 6 Plus

iPhone 6s

iPhone 6s Plus

iPhone SE

iPhone 7

iPhone 7 Plus

iPhone 8

iPhone 8 Plus

iPhone X

Will Your Battery Be $29 or Free?

If you're not sure if the iPhone model you have is still under a one-year limited warranty or AppleCare+ protection, visit Apple's coverage checker online. Just give them your device's serial number and it will let you know what coverages you have or had.

Can You Get More Than One Battery?

If you've already had your eligible iPhone's battery replaced under this program, you won't be able to take advantage of the offer again. While the program lasts until the end of 2018, it's limited to one repair per iPhone. If your iPhone is out of warranty and needs a second repair, that will cost $79.

Does the Battery Have to Be Failing?

You should also know that Apple may refuse to repair your battery if it does not have a replicable issue. While Apple does not address this problem on its site, Reddit users report that Apple technicians have turned away eligible iPhones whose batteries had not degraded below 79 percent. However, others have found success in replacing working batteries by simply being persistent.

Keep in mind that if you still have a one-year limited warranty, your battery will likely have to be failing since the warranty doesn't cover "consumable parts, such as batteries or protective coatings that are designed to diminish over time, unless failure has occurred due to a defect in materials or workmanship."

Save Money by Repairing in-Store

Apple lets you take advantage of the discounted battery replacement either in-store or by mail. While the latter might be more convenient for those averse to the Apple Store — or for those who live too far away from one — it will cost you; Apple charges $6.95 for out-of-warranty repairs that require shipping, bringing your repair cost to $35.95, before tax. If you want to retain the flat $29 fee when repairing your iPhone, make a trip to the Apple Store. If you'd spend more than $7 in gas getting there and back, well, maybe mailing is a better option after all.

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